In the inventor's experience, it occasionally happens that timing chains on vehicle engines will slip during operation due to timing gear wear or chain stretch. Frequently, the vehicle engine will still run, although performance is less than optimal, and will continue to run until accumulated chain slippage reaches a critical amount. When the engine thus runs poorly or stops, it is impractical to immediately adjust the timing chain to correct the chain slip. Of particular concern are military vehicles operating in a combat zone. My invention addresses the need for relatively instantaneous timing chain adjustment that obviates the need for tools, a special repair area and even the need to stop the vehicle. My invention works in concert with, or mechanically incorporates, a tension control mechanism that not only keeps a predetermined tension on the chain but also avoids stretching the chain beyond manufacturer tolerances or other chosen limit. The tension control mechanism can include means to detect a given degree of chain stretch and send an appropriate alarm signal when that degree of chain stretch occurs. Perhaps more importantly, the invention can also adjust engine timing during normal vehicle operation so as to maximize engine performance parameters such as power or fuel efficiency and minimized emissions, or to adapt the engine to varied types or grades of fuel. The adjustment can be automatic and powered by actuating mechanisms such as an electric motor, or a hydraulic or pneumatic cylinder, or other suitable conventional means. Additionally or alternatively, the adjustment can be manual and be accomplished with hand tools.
My invention is an engine accessory that acts during engine operation to retard or advance one or more engine cam shafts relative to the crankshaft by adjusting the timing chain that engages wheels on cam shafts and crankshaft. The accessory includes a rod translated by a hydraulic cylinder or an electric motor, wherein the cylinder or motor act in accordance with signals from an electronic controller. The controller itself responds to a human driver's input or to values of selected engine condition variables. At least one chain engagement wheel spins on either end of the rod. One chain engagement wheel meshes with the part of the timing chain approaching the crankshaft wheel while the other chain engagement wheel meshes with the part the chain travelling away from the crankshaft wheel. Translation of the rod affects the chain length between the crankshaft wheel and the camshaft wheels, thereby retarding or advancing the cam shafts relative to the crankshaft. The means for maintaining controlled tension on the chain can conventionally be a gear meshed with the chain and rotatable on a translatable rod mechanically forced or biased toward the chain wherein an alarm signal is triggered when the rod reaches a chosen position. Optionally, the tension control mechanism can be part of the accessory that retards or advances the cam shafts relative to the crankshaft.
It is contemplated that the invention can be used in a testing scenario wherein the engine and controller are not necessarily located in a vehicle but are mounted to a test stand. Various designs of engine components such as pistons, cam shafts and valves can be installed in an experimental engine. These components can be tested over a selected range of timing chain settings.